1. Field of the Invention
The present invention relates to an antenna apparatus and a communication system.
2. Related Art of the Invention
First, the configuration of an antenna apparatus according to the prior art will be described with reference to FIG. 20 and FIG. 21. FIG. 20 is a conceptual diagram providing comparative descriptions of a double-spiral antenna according to the prior art, a circular patch type antenna according to the prior art, and the composite antenna of the present invention. FIG. 21 is a conceptual diagram providing comparative descriptions of the performance characteristics of a double-spiral antenna according to the prior art and the composite antenna of the present invention.
First, the configuration of a double-spiral antenna according to the prior art will be described with reference to FIG. 20.
A spiral radiating element 107 has a feed terminal 105 that is given common termination via a sharing unit (not shown) and is connected to a reception input terminal (not shown) and a transmission output terminal (not shown) of a communication apparatus (not shown). The limit of the length L3 of the spiral radiating element 107 is about xc2xc of an electric wave wavelength. Therefore, when 1454 MHz is a resonance frequency, for example, the spiral radiating element 107 is designed so that a length L3 of the spiral radiating element 107 is approximately 51.6 mm.
A circular patch type radiating element 108 is located opposite the spiral radiating element 107. A limit of the circumferential length L4 of the circular patch type radiating element 108 is about xc2xd of the electric wave wavelength. Therefore, when the resonance frequency is 1513 MHz, for example, the circular patch type radiating element 108 is designed so that the circumferential length L4 of the circular patch type radiating element 108 is approximately 99.1 mm.
An inductance 109 is a metal tab for connecting the spiral radiating element 107 and circular patch type radiating element 108, and stabilizing a potential of the spiral radiating element 107.
A spiral parasitic element 110 is a part that does not have a feed terminal and is fitted parallel to the spiral radiating element 107. As shown in FIG. 21, the gain of an antenna that has a spiral parasitic element 110 (an antenna that has a double-spiral element), is better than the gain of an antenna that does not have a spiral parasitic element 110 (an antenna that has a single-spiral element).
The operation of a double-spiral antenna according to the prior art that has this kind of configuration will now be described with reference to FIG. 20. As the reception operation of a double-spiral antenna according to the prior art is understood as virtually the opposite of the transmission operation described below, only the transmission operation will be described below.
The transmission output terminal (not shown) of a communication apparatus (not shown) performs signal output to the spiral radiating element 107 via the feed terminal 105.
The electric field 155 generated between the spiral radiating element 107 and the circular patch type radiating element 108, due to the above described signal output from the communication apparatus (not shown), is sent as a transmission electric wave.
Next, the configuration of a circular patch type antenna according to the prior art will be described with reference to FIG. 20.
The circular patch type radiating element 108 has a feed terminal 105 that is given common termination via a sharing unit (not shown) and is connected to the reception input terminal (not shown) and transmission output terminal (not shown) of a communication apparatus (not shown).
An earth plate 104 is located opposite the circular patch type radiating element 108.
The operation of a circular patch type antenna according to the prior art that has this kind of configuration will now be described with reference to FIG. 20. As the reception operation of a circular patch type antenna is understood as virtually the opposite of the transmission operation described below, only the transmission operation will be described below.
The transmission output terminal (not shown) of the communication apparatus (not shown) performs signal output to the circular patch type radiating element 108 via the feed terminal 105.
An electric field 156 generated between the circular patch type radiating element 108 and the earth plate 104, due to the above described signal output from the communication apparatus (not shown), is sent as a transmission electric wave.
Incidentally, as shown in FIG. 20, a double-spiral antenna according to the prior art has good gain in the transmission band (1453 MHz to 1465 MHz), but does not have good gain in the reception band (1501 MHz to 1513 MHz). Also, as shown in FIG. 20, a circular patch type antenna according to the prior art has good gain in the reception band (1501 MHz to 1513 MHz), but does not have good gain in the transmission band (1453 MHz to 1465 MHz).
The present invention has been achieved by taking into account the actual problems described above, and it is an objective of the present invention to provide an antenna apparatus and communication system that enable high gain and an increase in specific-bandwidth to be achieved.
An antenna apparatus of the present invention comprises:
a first radiating element;
a second radiating element located opposite the first radiating element; and
an earth on the opposite side to the first radiating element with respect to the second radiating element, and opposite the second radiating,element,
wherein the first radiating element or the second radiating element is equipped with a feed terminal, and
electric fields are generated at least between the first radiating element and the second radiating element, and between the second radiating element and the earth, and electric wave transmission and reception is performed.
An antenna apparatus of the present invention comprises:
a first radiating element;
a second radiating element located opposite the first radiating element; and
a third radiating element on the opposite side to the first radiating element with respect to the second radiating element, and opposite the second radiating element,
wherein the first radiating element and the third radiating element are equipped with a feed terminal, and
electric fields are generated at least between the first radiating element and the second radiating element, and between the second radiating element and the third radiating element, and electric wave transmission and reception is performed.
A communication system of the present invention comprises:
an antenna apparatus including: a first radiating element; a second radiating element located opposite the first radiating element; and an earth on the opposite side to the first radiating element with respect to the second radiating element, and opposite the second radiating element,
wherein the first radiating element or the second radiating element is equipped with a feed terminal, electric fields are generated at least between the first radiating element and the second radiating element, and between the second radiating element and the earth, and electric wave transmission and reception is performed; and
a distributor for connecting the feed terminal to a communication apparatus for linear polarization and/or a communication apparatus for circular polarization.
A communication system of the present invention comprises:
an antenna apparatus including: a first radiating element; a second radiating element located opposite the first radiating element; and a third radiating element on the opposite side to the first radiating element with respect to the second radiating element, and opposite the second radiating element,
wherein the first radiating element and the third radiating element are equipped with a feed terminal, electric fields are generated at least between the first radiating element and the second radiating element, and between the second radiating element and the third radiating element, and electric wave transmission and reception is performed; and
a distributor for connecting the feed terminal to a communication apparatus for linear polarization and/or a communication apparatus for circular polarization.
As shown in FIG. 20 and FIG. 21, the antenna apparatus of the present invention, for example, uses an electric field which is the composite sum of electric field 155 and electric field 156 as transmission and reception electric waves, and has good gain in both the reception band and the transmission band.